A study published in the journal Science Advances reveals ice loss in the Himalayas has doubled in recent years.
Researchers from Columbia University compared recently declassified spy photos from the Cold War to modern images from NASA satellites to calculate the rate of ice loss over the last four decades. In total, they looked at 650 Himalayan glaciers, which combined span 2,000 kilometers (1,242 miles) east to west and represent 55 percent of the region's total ice volume.
The data shows that the region's total ice mass decreased by 13 percent between 1975 and 2000 and 28 percent between 1975 and 2016.
The glaciers have lost an average of 0.5 meters (1.6 feet) every year since 2000, with some regions seeing a jaw-dropping 5-meter (16-foot) drop per annum. Meanwhile, 8 billion tons of water (tantamount to 3.2 million Olympic-sized swimming pools) is being lost (on average) each year.
“This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” lead author Joshua Maurer, a PhD candidate at Columbia University's Lamont-Doherty Earth Observatory, said in a statement.
As the study authors point out, there are approximately 800 million people who rely on the yearly runoff for drinking water, electric power (hydropower), and farming purposes.
A study published earlier this year suggests that current runoff is 1.6 times greater than it would be if glaciers were restored at the same rate as they were melting, exacerbating the flood risk to downstream communities. And though there may be a "swelling" of runoff right now, this will decline in the coming decades as glaciers recede and experts forecast water shortages.
Indeed, scientists predict Everest could be devoid of ice as soon as 2100 – and the blame can be pinned on climate change. Using data collected by meteorological stations in the area, Maurer and his team show average temperatures in the Himalayas warmed close to 1°C between 2000 and 2016. While precipitation patterns and increased levels of soot play a role in ice loss, the researchers say climate change is the primary driver of accelerating melt.
The study shows that "even glaciers in the highest mountains of the world are responding to global air temperature increases driven by the combustion of fossil fuels," said Joseph Shea, a glacial geographer at the University of Northern British Columbia who was not involved in the study.
"In the long term, this will lead to changes in the timing and magnitude of streamflow in a heavily populated region."